Hi there,
we have a problem with an intranet that runs using plone 2.5.3

when users using IE want to open a zip file from the intranet by using
the "open" option from the download dialog they get winzip complaining
that the file is corrupted.
if they select "save" from the same dialog they can open the zip archive
without problem.
does anyone know a solution for this or give me an idea where to look
for one?

I had a similar problem with pdf files, and googling indicated that IE
might be deleting the cached copy of the document before the opening
application can get to it.

I have had some success setting cache control to "private". Something
like:

request.response.setHeader('cache-control','private')

"private,must-revalidate" may also be a good value, depending on your
situation.

I Googled back through and found that the problem usually manifests when
you have a 'cache-control':'no-cache' header. The above explanation was
not quite right.

Anyway, either removing the "no-cache" header or using one that allows
the local machine to keep a copy should work, if the problem is in fact
a 'no-cache' header.